For surfactants and surface treatment agents having fluorochemical chains longer perfluoroalkyl chains contain a higher percentage of fluorine at a given concentration and provide better performance. However, fluorinated materials are more expensive. Reduction of the fluorine content with delivery of the same or higher performance is therefore desirable. Reducing the fluorine content would reduce the cost, but it is necessary to maintain product performance.
WO 2005/113488 described fluoroalkyl/alkyl (twin-tailed) surfactants of the structure Rf—Z1—CH[(O)r—SO3M]—Z2—Rh in which Rf is a fluoroalkyl group that may have an ether bond; Rh is an alkyl group; r is 1 or 0; when r is 0, Z1 and Z2 respectively are —(CH2)n1—(X1)p1— and —(X2)q1—, and when r is 1, Z1 and Z2 respectively are —(CH2Y)p2—CH2— and —(CH2Y)q2—, wherein X1 and X2 are the same or different, and respectively are a divalent linking group; p1 is 0 or 1; q1 is 0 or 1; n1 is an integer of 1-10; Y is O, S, or NR (wherein R is H or a C1-C4 n-, iso-, sec-, or t-alkyl group); p2 and q2 respectively are 0 or 1 but were not all 0 at the same time; and M is H, alkali metal, half alkaline earth metal, or ammonium. These structures are disclosed as having surfactant activity in carbon dioxide, but no other media.
It is desirable to improve surfactant performance, in particular lowering surface tension in aqueous systems, and to increase the fluorine efficiency, i.e., boost the efficiency or performance of the surfactants so a lower proportion of the expensive fluorine component is required to achieve the same level of performance, or to have better performance using the same level of fluorine. Especially desirable would be surfactants with similar performance to current commercial products but having less fluorine present via shorter perfluoroalkyl groups. The present invention provides such surfactants.